forked from AbleScript/ablescript
Added support for specifying a tape size limit
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parent
99758a177b
commit
1306c797c8
77
src/brian.rs
77
src/brian.rs
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@ -2,7 +2,8 @@
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//!
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//! If you just want to execute some simple brainfuck, check the [`interpret_with_io`] function.
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//!
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//! To construct the interpreter, use the [`from_ascii`] or [`from_ascii_with_input_buffer`] methods. The latter grants access to
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//! To construct the interpreter, use the [`from_ascii`] or [`from_ascii_with_input_buffer`] methods
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//! (or their variants that take a maximum tape size). The latter grants access to
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//! the method [`add_input`], which allows for the addition of input while the interpreter is running.
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//!
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//! [`from_ascii`]: Interpreter::from_ascii
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@ -24,6 +25,9 @@ use std::{
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// NOTE(Able): This is the brain fuck interface
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/// The default limit for the tape size. This is the value used by methods that don't take it as a parameter
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pub const DEFAULT_TAPE_SIZE_LIMIT: usize = 30_000;
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#[derive(Debug, Clone, PartialEq, Eq)]
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/// A brainfuck interpreter. Read the [module level documentation](self) for more
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pub struct Interpreter<'a, I> {
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@ -31,17 +35,29 @@ pub struct Interpreter<'a, I> {
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instr_ptr: usize,
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tape: Vec<i8>,
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data_ptr: usize,
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tape_size_limit: usize,
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input: I,
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}
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impl<'a> Interpreter<'a, InputBuffer> {
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/// Construct an `Interpreter` from an ASCII string of code with an empty input buffer
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/// This methods sets the tape size limit to [its default value](DEFAULT_TAPE_SIZE_LIMIT)
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pub fn from_ascii_with_input_buffer(code: &'a [u8]) -> Self {
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Self::from_ascii_with_input_buffer_and_tape_limit(code, DEFAULT_TAPE_SIZE_LIMIT)
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}
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/// Construct an `Interpreter` from an ASCII string of code with an empty input buffer,
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/// setting the tape size limit to the specified value
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pub fn from_ascii_with_input_buffer_and_tape_limit(
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code: &'a [u8],
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tape_size_limit: usize,
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) -> Self {
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Self {
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code,
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instr_ptr: 0,
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tape: Vec::new(),
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data_ptr: 0,
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tape_size_limit,
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input: InputBuffer(VecDeque::new()),
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}
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}
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@ -53,17 +69,23 @@ impl<'a> Interpreter<'a, InputBuffer> {
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}
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impl<'a, I: BootlegRead> Interpreter<'a, I> {
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/// Construct an interpreter from an ASCII string of code and an source of input bytes
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pub fn from_ascii(code: &'a [u8], input: I) -> Self {
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/// Construct an interpreter from an ASCII string of code, a source of input bytes, and a tape size limit
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pub fn from_ascii_with_tape_limit(code: &'a [u8], input: I, tape_size_limit: usize) -> Self {
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Self {
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code,
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instr_ptr: 0,
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tape: Vec::new(),
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data_ptr: 0,
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tape_size_limit,
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input,
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}
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}
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/// Constructs an interpreter from an ASCII string of code, a source of input bytes, and [the default tape size limit](DEFAULT_TAPE_SIZE_LIMIT)
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pub fn from_ascii(code: &'a [u8], input: I) -> Self {
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Self::from_ascii_with_tape_limit(code, input, DEFAULT_TAPE_SIZE_LIMIT)
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}
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/// Advance the interpreter by one instruction.
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/// A return value of Ok(None) indicates succesful termination of the interpreter
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pub fn advance(&mut self) -> Result<Option<Status>, ProgramError> {
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@ -83,12 +105,16 @@ impl<'a, I: BootlegRead> Interpreter<'a, I> {
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}
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b'+' => {
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let val = self.get_or_resize_tape_mut();
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let val = self
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.get_or_resize_tape_mut()
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.ok_or(ProgramError::TapeSizeExceededLimit)?;
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*val = val.checked_add(1).ok_or(ProgramError::IntegerOverflow)?;
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}
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b'-' => {
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let val = self.get_or_resize_tape_mut();
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let val = self
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.get_or_resize_tape_mut()
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.ok_or(ProgramError::TapeSizeExceededLimit)?;
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*val = val.checked_sub(1).ok_or(ProgramError::IntegerUnderflow)?;
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}
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@ -98,7 +124,12 @@ impl<'a, I: BootlegRead> Interpreter<'a, I> {
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}
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b',' => match self.input.bootleg_read() {
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Ok(Some(num)) => *self.get_or_resize_tape_mut() = num,
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Ok(Some(num)) => {
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let cell = self
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.get_or_resize_tape_mut()
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.ok_or(ProgramError::TapeSizeExceededLimit)?;
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*cell = num;
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}
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Ok(None) => return Ok(Some(Status::NeedsInput)),
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Err(_) => return Err(ProgramError::InputReadError),
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},
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@ -157,11 +188,14 @@ impl<'a, I: BootlegRead> Interpreter<'a, I> {
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Ok(())
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}
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fn get_or_resize_tape_mut(&mut self) -> &mut i8 {
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fn get_or_resize_tape_mut(&mut self) -> Option<&mut i8> {
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if self.data_ptr > self.tape_size_limit {
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return None;
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}
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if self.data_ptr >= self.tape.len() {
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self.tape.resize(self.data_ptr + 1, 0);
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}
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&mut self.tape[self.data_ptr]
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Some(&mut self.tape[self.data_ptr])
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}
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fn get_at_data_ptr(&self) -> i8 {
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@ -251,6 +285,7 @@ pub enum ProgramError {
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InputReadError,
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UnmatchedOpeningBracket,
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UnmatchedClosingBracket,
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TapeSizeExceededLimit,
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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@ -308,6 +343,7 @@ mod tests {
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instr_ptr: 0,
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tape: vec![10, 5],
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data_ptr: 0,
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tape_size_limit: DEFAULT_TAPE_SIZE_LIMIT,
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input: std::io::empty(),
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};
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@ -323,14 +359,10 @@ mod tests {
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#[test]
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fn hello_world() {
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let mut interpreter = Interpreter {
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//Source: https://en.wikipedia.org/wiki/Brainfuck
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code: b"++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.",
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instr_ptr: 0,
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tape: vec![],
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data_ptr: 0,
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input: std::io::empty(),
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};
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let mut interpreter = Interpreter::from_ascii(
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b"++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.",
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std::io::empty(),
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);
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let mut string = Vec::new();
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interpreter
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@ -364,4 +396,17 @@ mod tests {
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);
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assert_eq!(interpreter.advance_until_io(), Ok(None));
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}
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#[test]
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fn hit_tape_size_limit() {
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let mut interpreter =
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Interpreter::from_ascii_with_tape_limit(b"+>+>+>+>+>", std::io::empty(), 1);
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let result = interpreter.interpret_with_output(std::io::sink());
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assert_eq!(
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result,
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Err(InterpretError::ProgramError(
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ProgramError::TapeSizeExceededLimit
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))
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);
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}
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}
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